Biological and algae harvesting and cultivation systems and methods
Algae harvesting and cultivating systems and methods for producing high concentrations of algae product with minimal energy. In an embodiment, a dead-end filtration system and method includes at least one tank and a plurality hollow fiber membranes positioned in the at least one tank. An algae medium is pulled through the hollow fiber membranes such that a retentate and a permeate are produced.
1. An algae harvesting method comprising:
in a dead end filtration process operating at or below atmospheric pressure, pulling a substantially algae-free permeate from an algae slurry through pores of a plurality of hollow fiber membranes positioned inside at least one treatment tank so that the permeate flows inside lumens of the plurality of hollow fiber membranes and a retentate of the algae slurry is produced outside the lumens of the plurality of hollow fiber membranes; and
in a backwash sequence, pushing a backwash fluid through pores of the plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes,
wherein the method includes (i) an interval of less than about three minutes, the interval defined as the time between the start of one backwash cycle and the start of a next backwash cycle and (ii) an off-line period of less than about twelve seconds, the off-line period defined as the time between an end of the dead end filtration process and a start of a next dead end filtration process.
2. The algae harvesting method of claim 1 , wherein (i) the algae slurry is a non-flocculated algae slurry having a first concentration of suspended solid algae, and (ii) the retentate has a second concentration of suspended solid algae that is greater than the first concentration, the second concentration equal to at least three percent solids content.
3. The algae harvesting method of claim 1 , wherein (i) the algae slurry is a non-flocculated algae slurry having a first concentration of suspended solid algae, and (ii) the retentate has a second concentration of suspended solid algae that is about fifty times greater than the first concentration.
4. The algae harvesting method of claim 1 , wherein at least about seventy-five percent of the suspended algae in the retentate is alive.
5. The algae harvesting method of claim 1 , wherein said pulling during the dead-end filtration process includes siphoning.
6. The algae harvesting method of claim 5 , wherein said pushing during the backwash sequence includes pushing gas accumulated in a siphon conduit through a purge conduit coupled fluidly to the siphon conduit.
7. The algae harvesting method of claim 1 , where said pushing during the backwash sequence includes gravity feeding the backwash fluid.
8. The algae harvesting method of claim 1 , wherein the backwash fluid includes at least one of a liquid and a gas.
9. The algae harvesting method of claim 1 , wherein the plurality of hollow fiber membranes are positioned in at least one treatment tank, and the at least one treatment tank includes (a) a plurality of treatment tanks in which each of the treatment tanks defines one stage of a plurality of filtration stages and contains at least one of the plurality of membrane filtration modules, or (b) at least one divider separating the at least one treatment tank into a plurality of filtration stages, each of the plurality of filtration stages containing at least one of a plurality of membrane filtration modules.
10. An algae harvesting method comprising:
isolating, using a first valve, a permeate suction source from a permeate outlet, the permeate outlet in fluid communication with an inside of lumens of a plurality of hollow fiber membranes positioned inside at least one treatment tank,
isolating, using a second valve, a backwash supply source from the permeate outlet, the backwash supply source configured to maintain a positive backwash pressure when the second valve is closed,
in a dead end filtration process operating at or below atmospheric pressure, pulling a substantially algae-free permeate from an algae slurry through pores of a plurality of hollow fiber membranes positioned inside at least one treatment tank so that the permeate flows inside lumens of the plurality of hollow fiber membranes and a retentate of the algae slurry is produced outside the lumens of the plurality of hollow fiber membranes; and
in a backwash sequence:
closing the first valve,
opening the second valve and immediately applying a backwash pressure to the permeate outlet and the lumens, and
pushing a backwash fluid through pores of the plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes,
wherein the method includes (i) an interval of less than about three minutes, the interval defined as the time between the start of one backwash cycle and the start of a next backwash cycle and (ii) an off-line period of less than about twelve seconds, the off-line period defined as the time between an end of the dead end filtration process and a start of a next dead end filtration process.
11. The algae harvesting method of claim 10 , wherein the permeate suction source is configured to maintain a permeate suction pressure when the first valve is closed, the method further comprising, at an end of the backwash sequence:
closing the second valve, and
opening the first valve and immediately applying a negative suction pressure to the permeate outlet and the lumens.
12. The algae harvesting method of claim 10 , wherein (i) the algae slurry is a non-flocculated algae slurry having a first concentration of suspended solid algae, and (ii) the retentate has a second concentration of suspended solid algae that is greater than the first concentration, the second concentration equal to at least three percent.
13. The algae harvesting method of claim 10 , wherein (i) the algae slurry is a non-flocculated algae slurry having a first concentration of suspended solid algae, and (ii) the retentate has a second concentration of suspended solid algae that is about fifty times greater than the first concentration.
14. The algae harvesting method of claim 10 , wherein at least about seventy-five percent of the suspended algae in the retentate is alive.
15. The algae harvesting method of claim 10 , wherein the backwash supply source includes a siphon.
16. The algae harvesting method of claim 15 , wherein said pushing during the backwash sequence includes pushing gas accumulated in a siphon conduit through a purge conduit coupled fluidly to the siphon conduit.
17. The algae harvesting method of claim 10 , where said pushing during the backwash sequence includes gravity feeding the backwash fluid.
18. The algae harvesting method of claim 10 , wherein the backwash fluid includes at least one of a liquid and a gas.
19. The algae harvesting method of claim 10 , wherein the plurality of hollow fiber membranes are positioned in at least one treatment tank, and the at least one treatment tank includes (a) a plurality of treatment tanks in which each of the treatment tanks defines one stage of a plurality of filtration stages and contains at least one of the plurality of membrane filtration modules, or (b) at least one divider separating the at least one treatment tank into a plurality of filtration stages, each of the plurality of filtration stages containing at least one of a plurality of membrane filtration modules.
20. The algae harvesting method of claim 10 , wherein the backwash supply source comprises a pump.
21. The algae harvesting method of claim 10 , wherein the permeate suction source comprises a pump.
22. The algae harvesting method of claim 10 , wherein the permeate suction source comprises an elevated tank, the elevated tank being elevated relative to the at least one treatment tank.